Method of coating



Aug. 13, 1935.

A. o. AUSTIN METHOD OF COATING Filed Jul 24, 1951 2' Sheets-Sheet 1 0 OHR N 0 R T 0 m T V n T m A Aug. 13, 19 35.

A. O. AUSTIN METHOD OF COATING Filed July 24, 1931 2 Sheets-Sheet 2INVENTOR F, Arf/rur 0. flasvf/n 9-6 62%},47 ATTORN Y Patented Aug. 13,1935 Jersey METHOD OF COATING Arthur 0. Austin, near Barber-ton, Ohio,asslgnor,

by mesne assignments, to The Ohio Brass Company, Mansfield, Ohio, acorporation of New Application July 24, 1931, Serial No. 552,815

7 Claims. (0191-) This invention relates to a process of galvanizingvarious forms of articles, especially rods, bars and structural shapesthat are elongated in form.

One of the objects of the invention is to provide a galvanizing processwhich will conserve the coating material.

Another object is to provide a coating process in which the coating willbe uniformly and thoroughly applied to the surface of the coated arti-.cle.

A further object is to provide a coating process which may be operatedcontinuously. I

A further object is to provide a process by which the coating may beeasily,'conveniently and effectively applied to articles which haveheretofore been diflicult to coat.

Other objects and. advantages will appear from the followingdescription.

The invention is exemplified by the steps of the process described inthe following specification and by the apparatus shown in theaccompanying drawings for performing'these steps. The invention is moreparticularly pointed out in the appended claims.

In the drawings:

Fig. 1 is a somewhat diagrammatic plan view sf one form of apparatus forpracticing the invenion.

Fig. 2 is a transverse section on line 2-2 of Fig. 1.

Fig. 3 is an elevation of a modified form of one portion of theapparatus.

Fig. 4 is a modified form of another portion of the apparatus.

Fig. 5 is an elevation of one, form of apparatus for performing asomewhat modified process.

.Fi 6 is a view similar to Fig.5 showing still another form ofapparatus.

Fig. 7 is a section on line 'I--'| of Fig 6.

Fig. 8 is an elevation on line 8-8 of Fig. 5.

In galvanizing structural steel shapes, reinforce ing rods, fence posts,and guy or anchor rods, it is frequently very difficult to galvanize theparts economically unless large volumes of material are used. This isdue to the fact that a very large or long galvanizing pot for holdingthe melted spel: ter is required; The present invention applies to anyprocess for coating the article with a fusible metal, such as zinc, leador tin. The method is particularly applicable to structural or othershapes which cannot be bent so as to deflect them into a galvanizingpot,but it may be used for wire, rods or cable which could normally bedeflected into a pot but which it is desired to galvanize in a straightposition.

With my improved method, it is possible to galvanize structural shapesof large dimensions with a very small amount of melted coating material.

Since the amount of coating material required is rather small, the lossdue to dressing, which is effected to a very considerable extent bymaterial dissolved from the large melting pot, is greatly reduced. Infact, in some cases, it is possible to use a continuous method so thatthe iron content in the melted zinc bath does not require drossing,thereby resulting in a material saving for a given thickness of coatingor weather-proofing.

Where a large pot is used to galvanize a few pieces, as has heretoforebeen the practice, the iron content of the molten zinc tending to causedross. is influenced more by the iron or steel dissolved from the potthan it is from the piece being galvanized; This is frequently a seriousfactor in the cost of galvanizing, particularly where the temperaturesof the bath are high.

The present invention comprises the steps of cleaning and fiuxing theobject to be coated and then driving the object through a stream ofmolten coating material. Following the coating of the article, theamount of coating material adhering thereto is reduced by a super-heatedair or gas jet, by rubbing means, or by a fiame and blast jet which willmaintain the piece at a fusing temperature while the excess material isbeing taken off.

Figure 1 shows one form of apparatus for practicing the invention inwhich a long object I ll is to be coated or galvanized. The object isplaced upon suitable rollers H for supporting it during the coatingprocess'and for driving it through the coating bath. After passingthrough the" coating bath, the object is picked up by rolls I2 or othersuitable conveyor.

The object is first cleaned and pickled, or, if desired, it may passthrough a sandblast hood l3 and then through a pickling or fiuxingchamber II. It then passes through a drying chamber i5 or it may passdirectlyinto the coating chamber l6. When the object goes into thecoating chamber l6, one or more revolving bucket or paddle wheels l'lrotated by a shaft [8 causes the melted coating material I 9 to flow orbe sprayed over the object to be coated. The metal IS in the tank isheated by jets 20, or electrically, or in any convenient way.

In order that all sides of the object l0 may be coated, it is rotatedduring its passage through the coating chamber by suitable drivingmechanism 2| and 22. In many cases, the rotating mechanism is notnecessary as the placing of the rolls II and I2 at an angle or thespiral twist in the work, as in the case of reinforcing rods, will causethe object to rotate as it passes through. This rotation may be atacontinuous rate or may be intermittent, or vary in degree, so as topermit coating and the throwing oil of excess material. In large pieces,such as angles, I beams and channels, it may be necessary to control thespeed of rotation in order that proper coating can be effected.

The object "I as it passes through the coating chamber, is subjected toone or more streams of coating material, either in the form of drops orin a steady stream, or, if desired, more than one coating chamber may beused, as shown at 2|. In general, however,it is preferable to have thefirst coating applied with as low a temperature as possible in orderthat amalgamation be started with a minimum amount of oxidation.Following this, ahigher temperature coating may be applied which willmake the coating material more fluid and thereby make it possible to usea thinner and more even coating, saving material and providing a finerfinish. To secure this result, the temperature may be'kept relativelylow in chamber l6 and higher in chamber 2|.

Where the temperature of the bath is not very high, a flux, such asammonium chloride or zinc chloride is used to flux the piece. Where thework is enclosed, this may be sprayed on as indicated at M, withoutserious difficulty as to spattering, the fluxing medium tending toinsure a good uniform coating and a smooth surface. The work issubjected to a second fiuxing in the chamber 22 before it enters thesecond coating chamber 2|. fine, light spray or as dry powder spray, sothat the work will not be wet when it enters the chamber 2| or, ofcourse, a second drying chamber like I! can be interposed between thechamber 22 and 2|.

Where it is desired to provide a thin coating, the object is subjectedto blast nozzles 23 which tend to drive off excess material as the rodor bar advances through the pot. Where a thin coating is desired, theblast nozzles are provided with super-heated air or with a flame,preferably at high velocity, or, at least, a portion at high velocity.Unless the air is super-heated, the expansion of the air lowers thetemperature and tends to cause the coating to become solid. The additionof the gas flame, however, makes it possible to maintain thetemperature, even though a supply of air or gas at normal temperature isused for the blast.

With pre-heated air, it is possible to use the supply of air over andover to conserve some of the heat of the blast and, what may be evenmore important, to maintain a neutral or inert atmosphere about the workto be galvanized or coated, thereby eliminating the eiIects ofoxidation. In this case, the supplyv of air is taken out through theopening 24, goes to a compressor and then back through the nozzles 23.

The chamber is provided with bailles 25 which prevent the splashing ofthe material out, particularly where the coating material is fed withsome considerable force. It is understood that the coating material maybe applied, either as a steady or smooth flow, or, by splashing themolten material on the object.

Any convenient way may be used to establish the easy fiow of material,such as a small paddle wheel for raising the material from .a lowerlevelto a higher level, after which it will flow over the piece. Another formof device, shown in Fig. 4, includes connected pots for holding themolten material above the work, the pots being pivotally mounted to tiltabout the work and alternately lifted, elevating the material whichpasses over the work from one pot to the other. The material may also belifted by a conveyor, or by a suitable centrifugal pump, or other means,

In this chamber the flux is applied in a.

Of course, it is necessary that all material used for handling thespelter in molten condition, be maintained at a temperature which willprevent it from solidifying. These parts may be'heated, if desired, ormay be maintained at temperature by the volume of molten materialpassing through. Where the material is elevated by a conveyor to amelting pot, it is not necessary that the material be in moltencondition when elevated.

In general, the hood of the coating chamber for a continuous process ispreferably maintained at a temperature which will cause the materialsplashing or falling on the sides to melt, so it may get back into thebath and be immediately re-used, or so it will flow into the conveyingequipment.

As the work advances and is cleaned, it is usually necessary andadvisable to solidify the coating before it touches any object. Unlessthis is done, bare spots are likely to result. An air blast 21 maybeused to congeal the material on the surface. On large objects, however,it will be found that while the surface is chilled, the heat from theinterior will cause melting of the coating a little later so it willeasily damage. This is particularly true where the advance of the workis rather rapid so that the cooling eifect is of short duration. Inorder to prevent trouble of this nature, it is necessary to lower thetemperature sufliciently so that thecoated object will not be damaged inthe later handling. In some cases, a series of cooling jets 21 or awater spray may be used.

Preferably, all cooling equipment should be placed in advance ofapparatus coming in contact for translating or rotating the object beingcoated. In some cases, it may be necessary to cool thr pieces graduallyby jets at the same time holding the material in position to preventwarping. In this case, the rolls must hold the pieces in position andthe cooling on the diiferent faces may be regulated by the jets so as toreduce the tendency to warp to a minimum.

The object to be galvanized may be placed in a horizontal position orinclined downward or upward as it passes through the coating chamber.Each type has special advantages. When the path is downward, thecleaning jet may blow the coating material back into the coating chamberand the fact that the article is inclined downward as it enters thecoating chamber, any flow of material over same will tend to be returnedto the pot. This may be of great advantage, particularly where the parthas longitudinal grooves or pockets which tend to retain quantities ofthe coating material.

If it is desired to omit the blast or means for regulating the thicknessof the coating or for removing excess material, the work may be inclinedupwardly'as it leaves the coating chamber. For this condition, it may benecessary to rotate the object to be coated sufllciently to throw oifmaterial so it will not run out of the coatingchamber, or to provide along coating chamber or one with a sufficiently long entrance to preventthe falling of the material outside of the pot or chamber, or .it may benecessary to use a blast which will prevent the material fiowingoutalong the piece where it enters the chamber. In this case, the blast maybe placed on the entering side in place of the exit, or, if desired,blasts may be placed on each side.

I The invention comprises the steps of subjecting the'object to becoated to a flow of coating material and giving the object a movementwith respect to the coating bath. The object may be inclinedto regulatethe flo'w and amount of coating or coatings of different temperaturesmay be used to facilitate the operating and control the thickness ofcoating.

To facilitate the work, cleaning jets are provided, as well .as chillingmeans. The object is cleaned and fluxed during the operation orseparately. If desired, the object may be subjected to fluxing meansbetween baths or in the coating chamber itself. Instead of nozzles 21, acircular pipe may encircle the work I0, having inner perforations fordirecting the jets against the work.

l The method is particularly applicable to galvanizing pipe, largecylinders and containers, particularly where it is desired to coat oneside only. Fig. 5 shows one form of apparatus for pplying the inventionto a large sized pipe in which a cylinder or pipe 30 is to be coated onthe inside. Mechanism 3| is provided for rotating the pipe or cylinder.The molten material is allowed to flow in at the upper end through aspout 32 and discharge at the lower end at 33. The cylinder may behandled in any enclosure which is heated in any convenient way, or wherethere is suflicient volume of material, the heating may be accomplishedby the flow of material itself. If desired, the blast cleaning systemmay be used on the coated surface, or the surface may be heated on theoutside by a series of jets. In this case, the coating is accomplishedover a small zone, the rotation of the member advancing the zone beingcoated untilthe object is completed Another method is to supply themolten material through a channel or duct system 36, as shown in Fig. 6.The coating material feeds back as the object is advanced and rotated.This method can be used for blind chambers or tanks, or may be used foropen end equipment, if desired, where a longitudinal heated zone mighttend to cause unnecessary warping. In this method, the coating zone isin the form of a spiral, making it possible to use much smaller cleaningblasts than where the long coating zone is used. The fact that a certainamount of material runs down over the surface and congeals in advance ofthe hot zone, can be used to advantage in obtaining an amalgamation oradherence of the coating before oxidation takes place.

If desired, some forms of work may be heated after passing through thecoating chamber, either by passing through a chamber which has asuflicient temperature, or by the flow of electric current through thearticle which will cause it to be heated.

I claim:

1. The process of coating an article with molten metal which will adhereto the surface of the article, the article being adapted for rotation,said process comprising the steps of feeding the article relative to a,coating station, flowing molten metal by gravity over the outer surfaceof the article at the coating station and rotating the article about anaxis extending in the direction in which it is fed to present differentportions of the article to 1 with molten metal which will adhere to thesurface of said article, said process comprising the steps of feedingthe article forwardly in the direction of the length thereof, causingmolten coating metal outer surface of the article as the article is fedforwardly and rotating the article about an axis extending in thedirection of the length thereof, to present various faces of the articleto the stream of coating material. 1

3. The process of coating an elongated article of definite length andadapted for rotation about a longitudinal axis, said process comprisingthe steps of causing liquid coating material to flow by gravity over alimited portion of the article, feeding the article forwardly to presentsuccessive portionsthereof to the bath of coating material, rotating thearticle to present different faces thereof to the coating bath anddirecting a blast or jet against the coated surface, to wipe saidsurface and regulate thacoating material thereon.

4. The method of coating an elongated article of definite length andirregular cross sectional contour comprising the steps of subjecting alimited portion of the article at a time to a bath of liquid coatingmaterial, feeding the article in the direction of its length throughsaid bath to present successive portions of the article to the coatingbath, rotating the article about an axis extending in the direction ofthe length thereof, to insure the application of the coating todifferent faces of the article and directing a wiping jet or blastagainst the surface of the article'as it moves away from the coatingbath, to regulate the coating of material on the surface of the article.

5. The method of coating the surface of an elongated article of definitelength and adapted for rotation about a longitudinal axis, said methodcomprising-the steps of feeding the article in a substantially straightpath through successive stations positioned in the path of the movingarticle, spraying the article with fluxing material at one of the saidstations, causing liquidcoating material to flow over said article at asubsequent station, rotating the article about an axis extending in thedirection of said path to subject all sides thereof to the flowingstream of coating material and directing a wiping blast or jet againstthe surface of said article at still another station.

6. The method of coating an elongated article of definite length andadapted for rotation about cleaning blast upon the article at onestation, spraying the article with fluxing material at a subsequentstation, causing coating material to flow over the article at anotherstation, rotating the article about an axis extending in the direc-'tion of said path to subject all sides thereof to the flowing stream ofcoating material, directing a -wiping blast or jet against the surfaceof said article as it leaves the coating station and cooling thecoatedsurface before it comes in contact with any solid object after it hasbeen subjected to said wiping blast or jet.

7. The method of coating an article comprising the steps of applyingliquid coating material to the article, directing a gaseous jet or blastagainst the coated surface, collecting the gas from said jet or blast,after it strikes the article, and again using the collected gas for saidjet or blast.

. ARTHUR 0. AUSTIN.

